In particular, the present invention relates to a curing device for tires comprising an upper half mold and a lower half mold connectable in releasable manner and defining a toroidal chamber for accommodating a tire to be cured and constituting part of a closed circuit for a batch charge of a heat exchange fluid; the circuit also comprising a delivery and a return conduit for the heat exchange fluid, connected to the toroidal chamber, and being assigned both powered means for force circulating the heat exchange fluid along the closed circuit, and heating means for heating the exchange fluid. A prior art curing device of the above type is described in U.S. Pat. No. 4,747,765, the content of which is fully incorporated herein by reference.
The curing device described in the noted patent comprises a central unit connected to the two half molds and housing both the forced circulating and heating means. The central unit is also designed in such a manner as to define both the delivery and return conduits for the heat exchange fluid. In the noted prior art curing device, the heating means consist of a heating element comprising a block of sintered material mounted inside the central unit and fitted through with a number of parallel, substantially axial channels defining part of the closed circuit and along which the heat exchange fluid flows from the toroidal chamber. Each channel houses an incandescent electrical resistor lapped directly by the heat exchange fluid, which is thus heated to the temperature required for curing a green tire housed inside the toroidal chamber.
In actual use, the heating element used in the aforementioned central unit has been found to result in relatively high hydraulic resistance capable of seriously decelerating the flow of the heat exchange fluid from the toroidal chamber. Moreover, immediately upstream from the inlet to the forced circulating means, the heating element creates such a swirl as to seriously impair the efficiency of the circulating means and, consequently, the acceleration imparted by the same to the heat exchange fluid. This swirl is transmitted downstream from the forced circulating means, thus resulting in further deceleration of the heat exchange fluid along the delivery conduit.
In the noted prior art curing device, the circulating means comprise a powered impeller, which, in addition to accelerating the heat exchange fluid, also provides for feeding it in a helical direction along the delivery conduit, so that it enters the toroidal chamber at a speed having a relatively high transverse component, i.e. directed circumferentially in relation to the toroidal chamber. The heat exchange efficiency of the heat exchange fluid and the green tire inside the toroidal chamber has in fact been found to be proportional to the speed at which the heat exchange fluid is circulated along the toroidal chamber and, therefore, to the transverse component of the speed at which the heat exchange fluid flows along the delivery conduit.
The main drawback caused by deceleration of the heat exchange fluid from the toroidal chamber, due to the type of heating device employed, by the poor efficiency of the circulating means, and by the resulting overpressure generated inside the delivery conduit, is that the speed at which the heat exchange fluid is fed along the delivery conduit presents a relatively low transverse component, thus resulting in a disturbed, substantially axial stream of heat exchange fluid along the delivery conduit.